1. Field of the Invention
The present invention relates to a roll film driving device capable, for different film cartridges, of selecting coupler means matched with the type of reel employed in said cartridge, thereby coupling the reel with the driving shaft and enabling forward and reverse rotation of the reel.
2. Related Background Art
The roll film driving device as described above is utilized, for example, in the microfilm reader and reader-printer etc., used for retrieval, reading and/or printing of the images on a reeled microfilm.
In such apparatus there have been employed at least two types of cartridge, i.e. an ANSI (American National Standards Institute, Inc.) standard cartridge, and an M-type cartridge proposed by Minnesota Mining and Manufacturing Co.
In the ANSI standard cartridge, the coupling member of the reel to the driving shaft is provided with a square hole formed at the center of the reel and having a radially extended engaging groove at a point in the internal periphery thereof, and the transmission of driving torque is achieved by inserting a square driving shaft into said hole, or by using a shaft with an engaging piece matching said engaging groove.
In the M-type cartridge, the coupling member of the reel is provided with a cylindrical recess of a relatively large diameter, formed at the center of the reel and having a pin hole on the bottom of said cylindrical recess, at a predetermined distance from the center thereof. A pin formed on an end flange face of the driving shaft engages with said pin hole, when said shaft is rotated while said flange face is pressed against the bottom, thereby transmitting the driving torque.
The above-mentioned two cartridges have almost the same external dimensions, but are different in the coupling structure with the driving shaft for driving the film takeup reel, and in the driving method for film feeding. For this reason there has been used an exclusive equipment for each type of cartridge, or an equipment usable for both types by interchanging an end part of the driving shaft. Thus, the former lacks the interchangeability of the cartridges, while the latter requires a tedious procedure of replacing said end part.
For resolving the above-mentioned drawbacks the Japanese Laid-open Patent No. 231533/1986 proposed an apparatus in which a driving shaft for the M-type cartridge is provided, around the end portion thereof, with the driving flange for the ANSI standard cartridge, wherein both driving members are simultaneously movable in the axial direction while said flange is retractable against a spring pressure along the driving shaft away from the reel. Also a pressing member with a tapered end is positioned, on the axis of said driving shaft, at a distance required for loading a reel from the end of said shaft and is biased by a spring toward said driving shaft thereby elastically supporting said reel. The above-explained apparatus can therefore be selectively adapted to both cartridges.
However, the mechanism proposed in the Japanese Laid-open Patent No. 231533/1986 explained above is still associated with following drawbacks:
(1) In using the ANSI standard cartridge, the position of the reel in the cartridge is very unstable since it is determined by the balance between the spring pressures at the flange of the driving shaft and at the pressing member, so that the reel flanges often contact the internal walls of the cartridge. Thus, the rotation of reel is associated with friction and abrasion, eventually leading to defective reel rotation and erratic film feeding; PA0 (2) In using the M-type cartridge, the pin on the driving flange engages with the pin hole formed on the bottom of the cylindrical recess of the reel to make the coupling, and the above-mentioned driving shaft, moving with said flange but not used in making said coupling, is accommodated in the space of the cylindrical recess of the reel. Consequently, the protruding length of said driving shaft, or the engaging length with the reel of an ANSI standard cartridge, is inevitably limited by the depth of the cylindrical recess of the reel of the M-type cartridge. In addition, since said driving shaft has a tapered end for facilitating the insertion into the reel of the ANSI standard cartridge, the effective engaging length of said shaft is further shortened to 1/3-1/4 of the length of the central hole of the reel. For this reason the supporting of the reel greatly relies on the function of the supporting member at the opposite side. Consequently, the reel is apt to be inclined, whereby the reel flanges come in contact with the internal walls of the cartridge, thus inducing friction and abrasion and eventually leading to erratic film feeding as in the case of the ANSI standard cartridge; PA0 (3) The driving flange for the M-type cartridge is biased by a spring provided on a hollow driving shaft for driving said flange, and a bearing cannot be provided for said hollowing driving shaft, as the external periphery thereof is utilized for said spring over a wide range. For this reason said hollow driving shaft has to be supported on one side only, and the resulting insufficient strength gives rise to the vibration of the center of said shaft.